P0446

P0446 Evaporative Emission Control System Vent Control Malfunction

CIRCUIT DESCRIPTION

DTC Detecting condition:

The vapor pressure sensor, VSV for Canister Closed Valve (CCV), VSV for pressure switching valve are used to detect abnormalities in the evaporative emission control system.

The ECM decides whether there is an abnormality in the evaporative emission control system by the vapor pressure sensor signal.

DTCs P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the components within the dotted line in Fig. 1 below, or when there is a malfunction in either the VSV for EVAP, the VSV for pressure switching valve or in the vapor pressure sensor itself.

Wiring Diagram:

CONFIRMATION READINESS TEST

First Trip Procedure
a. Vehicle must be cold, ambient temperature approximately between 50 °F - 95 °F.
b. Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) sensor almost same value.
c. Clear DTC's.
- Disconnecting the battery terminals or EFI fuse.
- Readiness tests will show INCMPL (incomplete).

d. Drive the vehicle according to LA#4 drive cycle. Note the state of Readiness Tests. They will change to COMPL as the evaluation monitors operate and if the system passes. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

Pass Condition - No Problem Found by the ECM
If the EVAP evaluation monitor shows COMPL, go to the Non-Continuous Test screen.

NOTE: Do not shut off the engine-the results will be invalid.

- To get there, go to Advanced OBD II, On-board Tests, Non-continuous Tests.
- If all of the tests in the time $02 category Tests show Pass, the evaluation monitor has operated and no problem was detected.

Fail Condition - Problem Detected by the ECM
If the EVAP evaluation monitor shows INCMPL, go to the Non- Continuous Test screen.

1. If all Tests show Pass, the following may have occurred.
- The EVAP evaluation monitor did not operate.
- The EVAP evaluation monitor did not finish.
- The ECM withheld judgement.

2. If one or more of the tests in the time $02 category show Fail, the EVAP evaluation monitor did operate and the ECM detected a problem.

3. Go to Continuous Tests screen. This is the only place DTC's are listed for the first trip.

NOTE: The DTC listed may not be valid. A second trip is needed to confirm the DTC.

Second Trip Procedure
a. Vehicle must be cold, ambient temperature approximately between 50 °F - 95 °F
b. Go to Readiness Tests screen.
c. Drive the vehicle according to LA#4 drive cycle. Note the state of EVAP evaluation monitor. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

d. If Readiness Tests changes to COMPL, the EVAP evaluation monitor has operated. Check for any stored DTC's.
- If a DTC has stored, the problem has been detected and confirmed by the ECM.
- If no DTC was found, the EVAP monitor operated but no problem was detected.

INSPECTION PROCEDURE

HINT:
- If DTC P0441, P0446, P0450 or P0451 is output after DTC P0440 or P0442, first troubleshoot DTC P0441, P0446, P0450 or P0451. If no other malfunctions than them malfunction is detected, troubleshoot DTC P0440 or P0442 next.
- Read freeze frame data using LEXUS hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.